1. Field of the Invention
The present invention relates to flexible boards and electronic devices, more particularly to a flexible board including a flexible body and a linear conductor provided therein and an electronic device including the same.
2. Description of the Related Art
As an invention relevant to a conventional flexible board, a high-frequency signal line described in, for example, International Publication WO 2012/073591 is known. The high-frequency signal line includes a dielectric element assembly, a signal line, and two ground conductors. The dielectric element assembly is formed by stacking a plurality of dielectric sheets. The signal line is provided in the dielectric element assembly. The two ground conductors are opposed to each other with respect to the signal line in the stacking direction. Accordingly, the signal line and the two ground conductors form a stripline structure.
Furthermore, one of the ground conductors has a plurality of openings overlapping with the signal line when viewed in a plan view in the stacking direction. As a result, less capacitance is created between the signal line and the ground conductor. Therefore, it is possible to shorten the distance between the signal line and the ground conductor in the stacking direction, resulting in a thinner high-frequency signal line. Such a high-frequency signal line is used, for example, to connect two circuit boards.
Incidentally, in the high-frequency signal line disclosed in International Publication WO 2012/073591, the dielectric element assembly is flexible and therefore is bent for use. FIG. 12 is a cross-sectional structure view illustrating a bent portion of the high-frequency signal line 510 disclosed in International Publication WO 2012/073591. FIG. 12 only shows the dielectric element assembly 512 and the signal line 520.
When the high-frequency signal line 510 is bent into an L-shaped shape, as shown in FIG. 12, a portion of the signal line 520 to the left of the bend and a portion of the signal line 520 below the bend are positioned closer to each other. Accordingly, floating capacitance is generated between the portions of the signal line 520 to the left of and below the bend. Such floating capacitance leads to the characteristic impedance of the high-frequency signal line 510 at the bend varying from a target impedance value.